Grinder pumps are often used in low pressure sewage systems for pumping sewage. A grinder pump is typically disposed in a sewage tank in which the grinder pump includes a motor for driving a grinder mechanism for cutting or grinding solids or semisolid matter in the sewage and a pump for pumping the processed sewage. Grinding solids and/or semisolid matter in the sewage allows the resulting particulate effluent to be transferred using a pump through relatively small diameter pipes without clogging.
Conventionally, grinder pumps are produced in two configurations, namely, an open wet well configuration and a closed wet well configuration.
In an open wet well configuration, a grinder pump is positioned inside a tank. The entire volume under the tank lid is considered as a single storage vessel for the wastewater that flows in and is periodically pumped out, i.e., there is no partition between the top and the bottom of the tank. Often the grinder pump is supported from the bottom of the tank on a stand.
In a closed wet well configuration, the grinder pump is located in a lower chamber of the tank that contains the wastewater flow. An upper chamber or accessway of the tank provides a passageway for the grinder pump to be installed and removed as needed. The accessway extends from the tank lid at grade level or ground level down to the upper plane of the wet well chamber. Typically in closed wet well configuration, an inwardly extending horizontal flange extends from the tank at the top of the wet well and has an opening large enough to accept the lower section of the grinder pump. The grinder pump assembly is suspended in the tank from an outwardly extending horizontal flange on the top of the grinder pump that rests on the inwardly extending horizontal flange of the tank. With the grinder pump in place, the outwardly extending horizontal flange of the grinder pump engages an inwardly extending horizontal flange of the tank around the aperture to create a continuous bulkhead separating the wet well from the accessway. Typically, often as many as twelve threaded fasteners are used to securely hold the grinder pump in place as well as provide the compressive force needed to effect a seal between the flange on the grinder pump and flange in the tank.
There is a need for improved grinder pumps, and particularly, means for securing and sealing the grinder pumps in closed wet well grinder pump stations.